Amazon dam devastates fish populations by 90%, local fishers report in new study

A comprehensive study reveals that the Santo Antônio hydroelectric dam has decimated fish populations by up to 90% in parts of Brazil’s Amazon region, fundamentally altering the lives of traditional fishing communities. The research, conducted by the Federal University of Amazonas in partnership with over 100 local fishers, documented the dramatic ecological impact following the dam’s 2008 construction on the Madeira River.

The dam’s disruption of the river’s natural flow has particularly affected key species including pirarucu, tambaqui, and pirapitinga—fish that have sustained Amazon communities for generations. “Fish need currents to navigate. They don’t need still water, they need moving water. And the Madeira River stopped flowing,” explained Raimundo Nonato dos Santos, a fisher from the Lago Puruzinho community in Amazonas state. Beyond the loss of fish, communities have struggled with prolonged periods of murky water that further disrupts the local ecosystem.

Researchers compared daily catch data from 2009-2010, before the dam’s completion, with data from 2018-2019, revealing the stark decline in both fish numbers and changes to traditional fishing patterns. The study highlights how large-scale infrastructure projects can profoundly impact indigenous and riverine communities who depend on healthy river ecosystems for their livelihoods. The findings underscore the ongoing tension between Brazil’s energy development goals and the preservation of Amazon biodiversity and traditional ways of life.